Instant messaging is a widely used service of which many different flavors exist. In general, instant messaging is a mechanism by which a user may send live or nearly instant messages to another user. In its simplest form, instant messages are text messages. Some systems enable live audio or video conferencing and can have file transfer, image viewing, and other features, including presence information, where the online status of a user may be communicated to another user.
Instant message services typically provide authentication through a user name and password. Once authenticated to the system, a user may interact with the instant messaging service through any terminal that has access to the internet. Some services enable a user to send and receive messages through a portable cellular phone, personal digital assistant, personal computer, or other network appliance.